It is generally known in the art to power turbines with gases being expelled from combustion chambers. These gas powered turbines can produce power for many applications such as terrestrial power plants. In the gas powered turbine a fuel, such as a hydrocarbon (for example methane or kerosene) or hydrogen, is combusted in an oxygen rich environment. The oxygen is generally provided from atmospheric sources which also contains nitrogen and other compounds. These combustion systems often have high emissions of undesirable compounds such as nitrous oxide compounds (NOX) and carbon containing compounds. It is generally desirable to decrease these emissions as much as possible so that undesirable compounds do not enter the atmosphere. In particular, it has become desirable to reduce NOX emissions to a substantially low amount and more preferably to a point where emissions are virtually eliminated. Emissions of NOX are generally accepted to be non-existent if they are equal to or less than about one part per million volume of dry weight emissions.
In a combustion chamber, fuel, such as methane, is combusted in atmospheric air where temperatures generally exceed about 1420° C. (about 2600° F.). This is especially true if flame holding zones or high temperature pilot flames are used to stabilize the combustion process. When temperatures are generally above about 1420° C., the nitrogen and oxygen compounds, both present in atmospheric air, undergo chemical reactions which produce nitrous oxide compounds. The energy provided by the high temperatures allows the breakdown of dinitrogen and dioxygen, especially in the presence of other materials such as various metals, to produce NOX or NOX compounds such as NO2 and NO.
Attempts have been made to reduce production of NOX compounds by initially heating the air before it enters the combustion chambers to an auto-ignition temperature. If the air enters the combustion chamber at or above an auto-ignition temperature, then pilot flames or recirculation flame holding zones are not necessary to combust the fuel. Auto-ignition temperatures are usually lower than pilot flame temperatures or the temperatures inside recirculation flame holding zones. One such method for heating air to the auto-ignition temperature is to mix the fuel in the air before it reaches the combustion chamber. This vitiated air, that is air which includes the fuel, is then ignited in a pre-burner where at least a portion of the entrained fuel is combusted. This raises the temperature of the air before it reaches the main combustion chamber. This decreases NOX production and emissions substantially. Nevertheless, NOX emissions still exist due to the initial pre-burning.
In view of the foregoing, it will be appreciated that it is desirable to decrease or eliminate pre-burning, thereby substantially eliminating all NOX emissions. Although the air is heated before entering the main combustion chamber, it may still need to be ignited in the combustion chamber to combust the remaining fuel. Therefore, an additional flame or arc is used to combust remaining fuel in the main combustion chamber. This reduces the temperature that the igniter must be at but still increases the temperature of the combustion chamber. In addition, no fuel is added to the air as it enters the combustion chamber. Rather all the fuel has already been entrained in the air before it enters the combustion chamber to be combusted. This greatly reduces control over where combustion occurs and the temperature in the combustion chamber.
Other attempts to lower NOX emissions include placing catalysts in catalytic converters on the emission side of the turbines. This converts the NOX compounds into more desirable compounds such as dinitrogen and dioxygen. These emission side converters, however, are not one hundred percent efficient thereby still allowing NOX emissions to enter the atmosphere. The emission converters also use ammonia NH3, gas to cause the reduction of NOX to N2. Undesirably, some of this ammonia is discharged into the atmosphere. Also, these converters are expensive and increase the complexity of the turbine and power production systems. Therefore, it is also desirable to eliminate the need for emission side catalytic converters.
Changing the flow path of a fluid, such as a gas, also is problematic. In particular, in many combustion systems, the flow of gases must be changed to move the fluid from an original direction or orientation to a second direction or orientation to properly operate the apparatus. For example, when an oxidizer is drawn from the exterior of the apparatus, it then generally must be redirected to a combustor. This can decrease the pressure as the flow of the fluid changes direction. However, the combustors operate most efficiently with a high pressure of the fuel and oxidizer in the combustion area. Therefore, it is desirable to produce a system that will allow for the fluids to change direction without substantially decreasing the pressure.